My applet is not showing up in a web page, and all of the code is correct...
I'll post it and the html code:
// import all need packages
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.applet.*;
//extend JFrame for the user interface and actionlistener for events
public class LCalcApplet extends JApplet implements ActionListener
{
/* create instance variables so they can be used in every method
* instance variables allow all method to use them, instead of only
* the method you are working in
*/
JButton btnCalc;
JTextField txtAmount;
JTextField txtAPR;
JTextField txtMonths;
JTextField txtPayment;
JLabel lblAmount;
JLabel lblAPR;
JLabel lblMonths;
JLabel lblPayment;
/* create a JMenuBar, used to hold the Menu's such
* as file, edit, and that kind of stuff...On top of that,
* you need the MenuItems...These are the actual items that show
* up on the drop down
*/
JMenuBar menuBar;
JMenu fileMenu;
JMenuItem exitItem;
JMenuItem resetItem;
//the classes constructor
public void init()
{
//create the menuBar
menuBar = new JMenuBar();
//create the items
fileMenu = new JMenu("File");
exitItem = new JMenuItem("Exit");
resetItem = new JMenuItem("Reset");
/* add all the items to the Menu, this is
* done by the add() method coorisponding to
* the JMenu class
*/
fileMenu.add(exitItem);
fileMenu.add(resetItem);
/* add action listeners to the menu items, this
* will enable us to peform action based on what was
* clicked.
*/
exitItem.addActionListener(this);
resetItem.addActionListener(this);
/* once all that is done, you add the
* menu to the menuBar, and then you set
* the menuBar to be used in the program...Note
* you do not have to add the menubar to the Container
* after setting it.
*/
menuBar.add(fileMenu);
setJMenuBar(menuBar);
/* JPanels are a type of container...
* It's good to use them as flow control,
* and to group controls
*/
JPanel row1 = new JPanel();
row1.setBackground(Color.white);
//add the amount textfield and label to the panel
lblAmount = new JLabel(" Purchase amount: ");
row1.add(lblAmount);
/* The JTextField requires one parameter,
* the number of characters long...So we use
* ten on these.
*/
txtAmount = new JTextField(10);
txtAmount.setBackground(Color.orange);
row1.add(txtAmount);
JPanel row2 = new JPanel();
row2.setBackground(Color.white);
//add the apr label and textfield to the panel
lblAmount = new JLabel(" Interest rate(APR): ");
row2.add(lblAmount);
txtAPR = new JTextField(10);
txtAPR.setBackground(Color.orange);
row2.add(txtAPR);
JPanel row3 = new JPanel();
row3.setBackground(Color.white);
//add the month textfield and label to the panel
lblMonths = new JLabel("Number of months: ");
row3.add(lblMonths);
txtMonths = new JTextField(10);
txtMonths.setBackground(Color.orange);
row3.add(txtMonths);
JPanel row4 = new JPanel();
row4.setBackground(Color.white);
//add the payment label and textfield to the panel
lblPayment = new JLabel(" Your payment is: ");
lblPayment.setForeground(Color.red);
row4.add(lblPayment);
txtPayment = new JTextField(10);
txtPayment.setBackground(Color.orange);
/* set this textfield so that it cannot be edited,
* because you don't want the user to enter anything
* in here.
*/
txtPayment.setEditable(false);
row4.add(txtPayment);
JPanel row5 = new JPanel();
row5.setBackground(Color.white);
//add the calculate button
btnCalc = new JButton("Calculate");
btnCalc.setBackground(Color.cyan);
/* add an actionListener to the button, this
* enables us to perform events if it was clicked
*/
btnCalc.addActionListener(this);
row5.add(btnCalc);
/* Construct a container object, and
* then add all of the JPanels to it.
* You set the layout to the container, so
* that you have some kind of flow control in the
* program.
*/
Container content = getContentPane();
//we will use a flowlayout
content.setLayout(new FlowLayout());
content.add(row1);
content.add(row2);
content.add(row3);
content.add(row4);
content.add(row5);
content.setBackground(Color.white);
//set the content pane of the frame
setContentPane(content);
//last, set it visible
setVisible(true);
}
public void actionPerformed(ActionEvent ae)
{
/* check to see if the event was fired by the
* calculate button, if so peform the correct operation
*/
if (ae.getSource() == btnCalc)
{
/* use some if/else statements to check and make sure
* that all the textfields have some value in them
*/
if (txtAmount.getText().equals(""))
{
JOptionPane.showMessageDialog(this,"Please enter an amount");
// invoke a class method that will show a simple message to the user
}
else if(txtAPR.getText().equals(""))
{
JOptionPane.showMessageDialog(this,"Please enter the interest rate");
// invoke a class method that will show a simple message to the user
}
else if (txtMonths.getText().equals(""))
{
JOptionPane.showMessageDialog(this,"Please enter length of months");
// invoke a class method that will show a simple message to the user
}
/* if we make it to here, all values are filled, and ready to be proccessed
* so we use a try cacth statement to make sure the values wasn't anything other
* than numeric.
*/
else
{
try {
//create new method used to calculate and show the monthly payment
getAndShowPayment();
}
catch (ArithmeticException mathE)
{
//catch an arithmetic exception, and if it was caught give the user
//some feedback
JOptionPane.showMessageDialog(this,"Error in arithmetic");
}
}
}
//just in case the selection was the exit item
else if (ae.getSource() == exitItem)
{
/* call the System classes exit() method, and
* place 0 inside of the paranthesis. This will make
* the program exit.
*/
System.exit(0);
}
//if the reset menu item was selected
else if (ae.getSource() == resetItem)
{
/* reset all the values in the textfields to null,
* we do this by callling the textfields setText() method
* and putting null values in there
*/
txtAmount.setText("");
txtAPR.setText("");
txtMonths.setText("");
txtPayment.setText("");
}
}
/* This is a custom method that returns void, or nothing...
* it will calculate the values, and print it out to the user
*/
public void getAndShowPayment()
{
/* Use the double's wrapper class(Double) to parse
* the text into a double...Do this for all three textfields
*/
double dAmount = Double.valueOf(txtAmount.getText());
double dAPR = Double.valueOf(txtAPR.getText());
double dMonths = Double.valueOf(txtMonths.getText());
/* This is the forumula to calcuate the mortgage:
* a -- loan amount
* m -- # of months to repay
* i -- monthly interest
*
*Monthly payment:
*
* a(i)
* -------- (divide)
* 1 - (1/1+i)^m
*/
/* this is the interest rate, we divide by 1200 because we
* want the user to be able to enter the intrest rate in this format:
* 6.5 instead of .065
*/
double rate = (dAPR / 1200);
//simply calculate the payment using the above formula.
double dgetMonthlyPayment = (dAmount * rate / (1 - (Math.pow(1 / (1 + rate), dMonths))));
/* use the decimal format class to create a new decimal format, this way the calculation
* will be to two decimal places
* we precede it with java.text because this is the class that contains the
* decimal format, and we don't to import the statement
*/
java.text.DecimalFormat dec = new java.text.DecimalFormat(",###.00");
//show the amount by calling the decimalFormat.format() method
txtPayment.setText("$ " + dec.format(dgetMonthlyPayment));
}
}HTML CODE
<HTML>
<HEAD>
</HEAD>
<BODY BGCOLOR="000000">
<CENTER>
<APPLET
code = "LCalcApplet.class"
width = "370"
height = "600"
>
</APPLET>
</CENTER>
</BODY>
</HTML>